An arrangement of layers with an oxide between a conducting layers and a semiconductor is usable as a portion of many of the structures used in semiconductor circuitry, such as capacitors, MOS transistors, pixels for light detecting arrays, and electrooptic applications.
The integration of non-SiO.sub.2 based oxides directly or indirectly on Si is difficult because of the strong reactivity of Si with oxygen. The deposition of non-SiO.sub.2 oxides on Si has generally resulted in the formation of a SiO.sub.2 or silicate layer at the Si .parallel. oxide interface. This layer is generally amorphous and has a low dielectric constant. These properties degrade the usefulness of non-SiO.sub.2 based oxides with Si. High-dielectric constant (HDC) oxide (e.g. a ferroelectric oxide) can have a large dielectric constant, a large spontaneous polarization, and a large electrooptic properties. Ferroelectrics with a large dielectric constant can be used to form high density capacitors but can not be deposited directly on Si because of the reaction of Si to form a low dielectric constant layer. Such capacitor dielectrics have been deposited on "inert" metals such as Pt, but even Pt or Pd must be separated from the Si with one or more conductive buffer layers.
Putting the high dielectric material on a conductive layer (which is either directly on the semiconductor or on an insulating layer which is on the semiconductor) has not solved the problem. Of the conductor or semiconductor materials previously suggested for use next to high dielectric materials in semiconductor circuitry, none of these materials provides for the epitaxial growth of high dielectrical materials on a conductor or semiconductor. Further, the prior art materials generally either form a silicide which allows the diffusion of silicon into the high dielectric materials, or react with silicon or react with the high dielectric oxide to form low dielectric constant insulators.
The large spontaneous polarization of ferroelectrics when integrated directly on a semiconductor can also be used to form a non-volatile, non-destructive readout, field effect memory. This has been successfully done with non-oxide ferroelectrics such as (Ba,Mg)F.sub.2 but not so successfully with oxide ferroelectrics because the formation of the low dielectric constant SiO.sub.2 layer acts to reduce the field within the oxide. The oxide can also either poison the Si device or create so many interface traps that the device will not operate properly.
Ferroelectrics also have interesting electrooptic applications where epitaxial films are preferred in order to reduce loss due to scattering from grain boundaries and to align the oxide in order to maximize its anisotropic properties. The epitaxial growth on Si or GaAs substrates has previously been accomplished by first growing a very stable oxide or fluoride on the Si or GaAs as a buffer layer prior to growing another type of oxide. The integration of oxides on GaAs is even harder than Si because the GaAs is unstable in O.sub.2 at the normal growth temperatures 450 C-700 C.